调用Runtime.getRuntime().exec(cmds)方法使用linux的tail命令

有没有熟悉java的runtime的么？通过调用Runtime.getRuntime().exec(cmds)方法使用linux的tail命令去拿回的inputstream流的长度是有限制的么？ 为什么我每次它只能最大给我传回来64k。。

 String cmd = null;
            if (logLineCount > 0) {
                cmd = "tail -n " + logLineCount + " " + filePath;
            } else {
                cmd = "cat " + filePath;
            }

            String[] cmds = new String[] {"/bin/sh", "-c", cmd};
            Process process = null;
            process = Runtime.getRuntime().exec(cmds);
            logger.debug("process: " + process.toString());
            if (process != null) {
                    InputStream in = process.getInputStream();
                    int size = in.available();
                    byte[] buffer = new byte[size];
                    in.read(buffer);
                    in.close();
                    result = new String(buffer, "UTF-8");
            }

if (process != null) {
process.waitFor();
InputStream in = process.getInputStream();
...